Boxes coated with citronella repel insects

Researchers have used the fragrant grass extract known as citronella oil to make food cartons that discourage insect infestation. The extract is an ingredient of perfumes and also an insect repellent in products already on the market. The oil kept beetles from entering containers during a test lasting several months.

Scientists with the research organization Ensis Papro in Rotorua, New Zealand, made cartons from cardboard that they had treated with one of five commercially available plant extracts. Previous research had suggested that insects avoid those extracts, which included oils of citronella, garlic, and pine needles.

Ken K.Y. Wong and his colleagues placed an unsealed paper bag containing wheat germ and muesli in each carton. Then, they put two of each kind of chemically armored box, two untreated cardboard cartons, and hundreds of red flour beetles in a large container.

Initial tests suggested that the beetles avoided only the citronella-coated cartons. In longer trials, the researchers then compared citronella-treated and untreated cartons. During the first 2 weeks, they found that half as many bugs entered the treated cartons as compared with the untreated ones. The citronella effect dwindled gradually and disappeared by 8 months, Wong and his team report in the June Journal of Agricultural and Food Chemistry.

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